94LT1 . replaced radiator, thermastat, hoses. and belt. no visable leaks. after filled up a day or two later it over heats and have to add water. any idea what the problem is????????

 

air pockets, they are very hard to get out sometimes. blame the reverse flow coolant system. When you fill it next time take the hoses off of the water pump and fill them then quickly put them back on. Then open the bleeder screws on the water pump neck, let it run until the thermostat opens and all the air is out let the coolant run right out f the bleeder screws until it is constant coolant. Might want to have a few old towels around to save the optispark. Close the bleeder screws and drive it up the road. Slam on the brakes and take off several times really hard to dislodge any last lingering air pockets. This is one of the most difficult basc maintenance problems with our cars. You might not need to do this because if you overheated and added coolant then you may have found the air pocket and gotten it out already. Open the bleeder screws and let it run until coolant comes out only then close.

 

Thanks alot, ill give it a try

 

yep try bleeding it. there are three bleeder valves. brass screws that u will see one under the tb, one on the thermostat housing and one in the hose by the alternator. start with the lowest and end with the highest. the highest one by the alt likes to be bleed while the motor is running. it works good for me if i park the car on the steepest incline with the front of the car up then bleed and refill. start the car bleed again, take the car for a ride a few blocks up the road and back and do it one more time.

 

also i should mention it runs rough when i first start it up it didnt do that till after i replaced everything?

 

First off, I hope the opti is not getting leaked on, which would be a reason the car is running rough. I'm assuming you bled the system by now based on the other replies. If your car is still overheating, let's try to narrow down what the problem with the following questions.

1) Did you have an overheating problem before you replaced all of the components you mentioned? Be sure you put everything back on nice and tight. My radiator initially leaked after I replaced it becuase I didn't put the low coolant level sensor back on tight enough.

2) Are your fans coming on when the car begins to overheat?

3) Are there any squealing noises or leaks near the water pump? If the water pump is going bad, it may be leaking on the opti, causing your car to run rough (let's hope this is not the case).

4) Are you getting a strong coolant flow out of your upper radiator hose? After the car reaches operating temperature and the thermostat opens, the upper radiator hose will begin to feel hot. If you try to squeeze the hose with a glove on and let go, you should feel a rush of coolant, indicating a working water pump and thermostat. If you try to squeeze the hose without a glove, ensure there is no one around to make fun of you after you burn your hand.

5) Does you lower radiator hose feel cool after the thermostat has opened and your car has reached operating temperature?

There are other things to check (i.e. radiator cap), but we should be able to greatly narrow the problem if you are able to answer the questions I listed. Also, I want to emphasize what 383Stro said about using towels to prevent coolant from getting on the opti when you bleed the system.

Of course, I have to provide a link to this website http://shbox.com/1/4th_gen_tech2.html#cooling.